1. Field of the Invention
The field of the present invention is that of turbine engines and, more particularly, that of devices associated with the bleeding of air which is effected on these turbine engines.
2. Description of the Related Art
The main purpose of turbine engines is to produce thrust or supply power to a vehicle, such as an aircraft, but they also often have the additional function of supplying pressurized air in order to carry out a number of auxiliary functions which are necessary for the satisfactory operation of this vehicle. Two main types of auxiliary function are known, one in which power is drawn off from a shaft driven by the driveshaft of the turbine engine and one in which air is bled at the outlet of one of the stages of the compressors of the turbine engine. This pressurized air can be used, for example, for the air conditioning of the cabin, for pressurizing the fuel tanks and for other functions, these functions being together known by the name ECS (Environmental Control System).
The air is generally bled from a cavity situated downstream of the last compressor where the flow is tranquilized before it exits the turbine engine. It is then conveyed, via a bleed pipe, to the various elements of the aircraft which make use of it.
In turbine engines where the last stage takes the form of a centrifugal compressor, the flow is straightened by a diffuser in order to direct it substantially in the axis of the combustion chamber. A diffuser is a cylindrical part which collects the air as it exits the turbine wheel of the centrifugal compressor and which straightens it so as to direct it in a substantially axial direction.
When air is bled as it exits the last compression stage, the tranquilization chamber is generally situated upstream of the centrifugal compressor so as to make optimum use of the space. The flow of air which has been bled then needs to pass through the radial barrier formed by the wheel of the diffuser. Devices for bleeding air at the diffuser have been conceived, in the form of a tapping point situated either on the upstream face of the diffuser, or at its radial end, such that the air which has been bled does not have to pass through the wheel of the diffuser. But this solution has the major disadvantage that it does not separate the air from the dust which it conveys and that this dust is present in the tranquilization chamber and is carried into the pressurization circuit of the aircraft. Another solution was then conceived, which consists in bleeding the ECS conditioning air downstream of the diffuser, from the inlet cavity of the combustion chamber, and in passing it through a particular circuit so as to forward it to the tranquilization chamber. This solution, which generally consists in bypassing the diffuser on the outside, entails an increase in the weight of the turbine engine.